Products > Test Equipment

DMM with THD capabilities

<< < (4/5) > >>

pope:
The QuantAsylum QA403 (or rather the QA404) is in my list but I'm not sure yet. BTW, the 404 won't have isolation...

There's also the autoranger by linear audio but as I said I anted to ask if a commercial DMM with THD exists but it looks like the answer is no. t least for the specific requirments.

I currently use an audio interface with REW as well as some other pieces of software and I'm totally fine with the results but I as hopping for a standalone option that can also withstand higher voltages.

BTW, I don't do power amps. I'm mostly into pro audio gear.

elecdonia:
My opinion here is based on my 40+ year career repairing, restoring, and designing home, pro-sound, and musician audio equipment.

For most troubleshooting, repair, and restoration of audio gear, a distortion test rig with residual THD of .01% will suffice. By “residual distortion” I am referring to directly measuring the output of the audio oscillator with the THD analyzer. The most sensitive range on the THD analyzer should be .1% THD full scale or better. Most units with .1% full-scale will have residual distortion about 10 times lower, .01-.015% THD is typical.

I haven’t used a Keithley 2015THD myself. It has a good reputation as a self-contained THD measurement system.

Other complete “one-piece” audio oscillator/THD analyzer systems to consider:
Hewlett-Packard 8903A. There is also the 8903E model which omits the internal audio oscillator. The HP 8903 series is legendary among 1980-vintage audio test gear. I intend to get one myself if I find one at the right price.
Sound Technology 1701A distortion measurement system. Another legendary THD analysis system from the 1980 time frame. I own one. It is my primary THD measurement system. It’s residual THD is .0015%. That’s about as good as it gets for a pure analog measurement system.
Audio Precision System One.This is the first among a large family of high-performance digital audio analyzers. These work with a PC or laptop. They are capable of measuring THD and much, much more.

If your budget is limited it is still possible to find older (1970’s vintage) pre-owned separate THD analyzers and audio oscillators with adequate performance. Brands/model numbers to look for include:
THD analyzer: HP 333A, HP 334A, HP 339A. I own a HP 334A. It was my primary THD analyzer before I got the Sound Technology 1701A
Audio oscillator: I have a Krohn-Hite 4300A ultra-low distortion audio oscillator. Another good Krohn-Hite model is the 4400A.

jasonRF:

--- Quote from: JohanH on January 03, 2023, 04:44:01 pm ---Check the diyaudio forum, soundcards seems the way to go

https://www.diyaudio.com/community/threads/howto-distortion-measurements-with-rew.338511/

Disclaimer, I don't know anything about the software referred to, I imagine there are other alternatives, too.

--- End quote ---
I have used REW, just as shown in that thread on diyaudio.  In the first few pages you will see examples from $120 (US) and $45 (US) audio interfaces and see how well they do.  Even the cheap audio interface will be better at THD measurements than the overwhelming majority of scopes.

I would not expect the soundcard/REW approach to be as good as you get with audio analyzers, but it is within the budget of even casual hobbyists.

Jason

bson:
If you insert a 1kHz notch filter and apply a 1kHz test tone, then the DMM set to ACV RMS will measure THD+N RMS.  Divide by the test tone RMS level and you have it as a fraction.

pope:
Many good recommendations. I need to do my homework! Thank you  :)

Navigation

[0] Message Index

[#] Next page

[*] Previous page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod